One-year prophylactic treatment of euthyroid Hashimoto's thyroiditis patients with levothyroxine: Is there a benefit?

Studies in animal models of spontaneous Hashimoto's autoimmune thyroiditis (HT) show that prophylactic treatment with levothyroxine (LT4) can reduce i ncidence and degree of lymphocytic infiltration in HT. The aim of the prese nt study was to clarify whether there is a benefit of prophylactic treatmen t with LT4 in patients with euthyroid HT with respect to the progression of the autoimmune process. Twenty-one patients with eu thyroid HT were checke d for thyroid function (thyrotropin [TSH], free triiodothyronine [FT3], fre e thyroxine [FT4]), thyroid volume, antibodies (thyroglobulin [Tg-Ab], thyr oid peroxidase [TPO-Ab]), and lymphocyte subsets. Peripheral (PBL) and thyr oid-derived lymphocytes (TL) were analyzed by triple color flow cytometry. One-half of the patients with euthyroid HT were treated with LT4 for 1 year (n = 10). The other half (n = 11) were never treated with LT4. TL were obt ained by fine-needle aspiration biopsy (FNAB). Thirteen healthy subjects (C ) without medical history of thyroid disease serc ed as controls concerning PBL, and patients with nontoxic nodular goiter (NG; n = 10) served as cont rols concerning TL. Thyroid-derived TT-helper cells were found more frequen tly in euthyroid patients with HT compared to patients with NG (p < 0.01). After 1 year of therapy with LT4, TPO-Abs and B lymphocytes decreased signi ficantly only in the treated group of euthyroid patients with HT (p < 0.05) . In contrast, TPO-Abs levels did not change or even increased in untreated euthyroid patients with HT. Thyroid volume did not differ before and after therapy. Prophylactic treatment of euthyroid patients with HT reduced both serological and cellular markers of autoimmune thyroiditis. Therefore, pro phylactic LTB4 treatment might be useful to stop the progression or even ma nifestation of the disease. However, the long-term clinical benefit of prop hylactic LT4 therapy in euthyroid patients with HT is yet to be established .